Problem: $\dfrac{1}{5} + \dfrac{2}{4} = {?}$
Solution: ${\dfrac{1}{5}}$ ${\dfrac{2}{4}}$ $+$ ${\dfrac{1 \times 4}{5 \times 4}}$ ${\dfrac{2 \times 5}{4 \times 5}}$ $+$ ${\dfrac{4}{20}}$ ${\dfrac{10}{20}}$ $+$ $ = \dfrac{{4} + {10}}{20} $ $ = \dfrac{14}{20}$